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This website has been created by and is supported by a group of Boston, MA - area amateur astronomers. It is intended to be a convenient site to access news and information about astronomy and space-related activities of interest to the community and the public.



The skies of October yield a bounty of riches


October has a lot going for starwatchers and other appreciators of nature at night. Never mind this weekend’s rain; October nights are especially clear on average. Darkness arrives early, the hazes and mosquitoes of summer are mostly gone, but it’s not yet winter.

So what’s to see up there these evenings? It depends where you look.

The whole southeastern side of the sky appears almost blank through the light pollution inside Route 128. This celestial realm is known as the Great Water, home to big, dim, water-themed constellations: Capricornus the Sea Goat, Aquarius the Water Pourer, Pisces the Two Fish, and just nosing above the horizon, Cetus the Whale.

Good luck picking them out.

Elsewhere things are more interesting. Turn east and face high, and unless your light pollution is truly awful, you’ll find the Great Square of Pegasus, emblem of fall. It’s part of the flying horse of Greek myth.

Look for a square a little larger than your fist held at arm’s length, tipped up onto one corner.

The Square is supposed to be the front half of the horse’s body. Save the rest for a night in country darkness.

From the square’s left corner, a line of three or four stars extends left and slightly down. This is the profile outline of Andromeda, damsel in distress of Greek legend. The left-corner star is her head, the rest of the line is her backbone and one leg, the other, dimmer leg is raised and bent at the knee, and her outstretched arm is supposed to be chained to a rock. We’ve drawn her whole big stick figure in case you have a dark enough sky to piece it out this week or next.

Andromeda is most famous for what’s just off her upraised knee. Look for a hazy little dim-gray glow, like an escaped oval tuft of Milky Way.

The tuft looks like that for a reason. It’s the Great Andromeda Galaxy, an approximate twin of our own Milky Way Galaxy but 2.5 million light-years distant. If any creatures there have eyes like ours and clear nights, they’re seeing our own galaxy looking about like that.

A pair of binoculars makes it easier to spot, but even the view in a telescope is underwhelming from Eastern Massachusetts. It doesn’t look like the enormous thing, striped with two black bands, that 19th- century astronomers drew before photography revealed its true form.

Last summer I got a proper view, black stripes and all, from the Summer Star Party — a big annual amateur-astronomy gathering in Plainfield, in the dark northern Berkshires. A group of New York amateurs brought a towering 20-inch telescope. Lines of people at night waited to climb a tall stepladder to its eyepiece.

The Andromeda Galaxy was, finally, breathtaking.

But it still was nowhere near as clear as a photograph.

The fact is, our eyes are not meant for looking into space. They evolved to work with things right around us on Earth, things that might affect us. The stars don’t. So it’s a lucky fluke that we can see them at all.

The invention of photography was a turning point for astronomy. Today you can find dazzling observatory photos by the thousands. But what you’re looking at is what you would see if you had eyeballs as big as houses, with light-gathering pupils as wide as garage doors, and electronic retinas thousands of times more sensitive than the retinas nature gave you. And swappable retinas that work in the infrared and ultraviolet where humans can’t see.

So, that dazzling Hubble Space Telescope panorama of the Eta Carinae Nebula is not what you would see even if you were right there looking out the window of a starship. It’s what the camera system of the Hubble would see looking out the window.

Alan M. MacRobert is a senior editor of Sky & Telescope magazine in Cambridge ( His Star Watch column appears the first Saturday of every month.


Glorious view of Venus as it draws close to us

“What’s that . . . thing?” my wife, Abby, called from the front step last week. It was late twilight, and she was looking west. “There in the sky.”

“Must be Venus,” I called back.

“I know Venus,” she replied. “This is too bright.”

Abby knows the sky. She can spot Delphinus, the Teapot, the wound on the flank of the Bull, and much else. When we met, the care and attention with which she examined the globular cluster M13 though my telescope helped me realize she was a keeper.

I went and looked. It was Venus. But the night was especially clear, and Venus has been brightening and climbing high into thinner air this spring. It was unusually striking. And in May it brightens a little further.

Venus is swinging along its fast orbit around the Sun and catching up with the slower Earth. Right now it’s heading almost straight at us.

That’s why it’s getting bigger and brighter. But come June, it will start to curve away and head down toward the sunset, on its way to passing between us and the sun in August.

Venus isn’t all that big — it’s slightly smaller than Earth. But it’s closer to us than any other planet most of the time, and its global blanket of white cloud is lit by sunlight almost twice as bright as sunlight on Earth. So it can be quite a show.

Shining very high to Venus’s upper left this month (off the chart here) is another cloud-covered planet: giant Jupiter, taking second place for brightness and perhaps jealous of Venus. It’s 12 times bigger in diameter, but it lives seven times as far from the sun where the illuminating light is only 2 percent as bright.

Look way down to Venus’s lower right in twilight this week and there will be a third planet, Mercury. It’s only half Venus’s size, and its surface is dark gray. But sunlight on it is almost twice as intense as even at Venus, which is why we see Mercury as much of anything at all.

Watch Mercury fade day by day; it’s showing us more of its night side as it moves in orbit. If you have very clear air, binoculars may show the Pleiades star cluster to Mercury’s right this weekend. Aldebaran, the eye of Taurus the Bull, twinkles left of Mercury and straight under Venus. Like Capella high to Venus’s upper right, it’s a giant sun shining by light of its own, hundreds of thousands of times farther away.


Star Watch
Good news about exoplanets could be bad news for us
Last month Venus paired up with little Mercury low in the fading glow of sunset. Now Venus is about to pair up with little Mars. But this time they’re higher in better view.
Venus is the brightest celestial object after the sun and moon. It’s creeping higher week by week in the western twilight, on its way to a dazzling performance high in the west as the Evening Star this spring.
Mars, by contrast, is beginning to sink down and away after hanging low in the dusk since last summer. Look carefully; it’s less than 1 percent as bright now as Venus. This is because Mars is smaller, it’s farther from the sun so it’s less brightly lit, it’s covered with rusty-dull rocks and soil compared to Venus’s bright white clouds, and Mars is nearly 50 percent farther away as you look at the two planets through your drive-time windshield this week.
Yes, you can be an astronomer while commuting. In short glimpses anyway.
Is it good news or bad news?

Planets continue to make the news in new ways all the time. And with almost every finding that some observatory or institution announces to the public, there comes the obligatory comment on what this might mean for life in the universe. Most of these comments are brief and simplistic. But we shouldn’t become jaded; this is a real and important topic, and it becomes more overwhelmingly important to the human future the farther into the future you care to look.
Two exoplanet findings that were announced in the last two weeks are either good or bad news for mankind, depending on how you think. On the one hand they are genuinely positive for how abundant living worlds may be throughout the universe.
On the other hand, one of them in particular is profoundly unsettling in what it hints about our own future.
The first finding was theoretical, worked out by modeling the interactions of suns with their planets in extreme circumstances. The suns in question are red-dwarf stars, the dimmest and most abundant stars in the cosmos.
They’re dim enough that planets would have to huddle close to them to receive comfortable, liquid-water warmth. Fortunately, this is what the planets of such small, low-mass stars tend to do.
The catch: a world orbiting so close to a red-dwarf star should have its atmosphere stripped away by the outbursts and flares that happen early in such a star’s life.
But nature leaves a way to get through this fix, Rodrigo Luger and Rory Barnes of the University of Washington reported on Jan. 28.
A planet that starts off more like Neptune than Earth — that is, a massive body that’s mostly atmosphere — can have most but not all of its gas stripped away by the young red dwarf, leaving a world parked in the right place that’s more or less a good Earth.
The idea may sound simple, but the details were a bear. Such a lucky outcome might be unusual, but there are so many red dwarfs swarming among the brighter stars, and so many of them are proving to have exo-Neptunes, that the sheer numbers make the scenario look good.
If we ever get a radio wake-up call from another civilization, this is the kind of world it may come from.
The other news, released on Jan. 27, is more sobering. It too deals with the worlds of a dwarf star. Yale planet hunters Sarbani Basu and Debra Fischer untangled the signs of five planets, all roughly Earth-size, periodically crossing the face of the star Kepler-444. We observe this happening by a stroke of luck: their orbits appear exactly edge-on from Earth’s point of view.
Other exo-solar systems like this were already known. The remarkable thing about this one is the age of the star: 11.2 billion years. That’s much older than our 4.6-billion-year-old sun and solar system. Kepler-444 and its planets formed when the universe was less than 20 percent of its present age.
Astronomers had not known that rocky, Earth-like planets could form so early in cosmic history. The heavy elements that make up the bulk of a good world — iron, silicon, oxygen, magnesium, and other rock-forming elements — accumulated in the universe only gradually.
They emerge only from the smoke and ashes of dead stars that cooked them up from hydrogen in their nuclearreactor interiors. Material from the early universe is quite deficient in such elements. But clearly now, there was enough to make rocky planets anyway.
In fact, astronomers estimate that a majority of the Earths in the Milky Way have a billion or two years’ head start on us.
Why is this so sobering for our future? Because it removes what used to be a tidy explanation for a troubling mystery. If the universe is full of life-friendly planets, and if life often evolves to intelligence and space travel as it has done here, the mystery is why aren’t we already overrun with waves of aliens? Since ages and ages ago? One theory was that we’re among the first; others haven’t had time yet to evolve and spread very far. But now that explanation is shot to pieces.
The fact that Earth hasn’t been a constant busy alien spaceport since the Precambrian Era is an aspect of the Fermi Paradox, named for the nuclear physicist Enrico Fermi, who in 1950 pointedly asked, “Where are they?”
Clearly, something prevents the development of abundant advanced life that builds interstellar spacecraft. And we don’t know what it is.
Will it apply to us? 

Alan M. MacRobert is a senior editor of Sky & Telescope magazine in Cambridge ( His Star Watch column appears the first Saturday of every month.









Orion the Hunter, bright and distinctive even through city sky glow, is the best-known of the 88 constellations that cover the sky. You'll find Orion climbing the southeastern heavens at this coldest time of the year. Sirius, his Dog Star, follows brightly down below. The planet Jupiter, even brighter, glares off to Orion's left this season.

Even if you've never recognized Orion before, you may have noticed Orion's Belt, the eye-catching row of three stars in his middle. They look like such a neat row up there in space. In fact, they're not. The stars of Orion's Belt are at different distances from us and, if you could see them from the side, would form some kind of very unrelated-looking arrangement.

But here's the rub. Even in this age of precision spaceflight, a thousand known exoplanets, and a date for the Big Bang that's accurate to 1 percent, astronomers still have such poor information on the distances to most stars that we don't know how Orion's Belt is really arranged.

It's a problem all over the sky.

Two weeks ago, the European Space Agency launched a specialized space observatory to fix the star-distance problem with spectacular thoroughness. The mission is named Gaia. It promises to revolutionize not just this one field but, because star distances are fundamental to nearly everything else we know beyond the solar system, much of the rest of astronomy, too.

Its Dec. 19 launch received little attention. But once Gaia settles into its assigned post far from Earth, it will start measuring star positions, an ancient endeavor called astrometry, with extraordinary new precision and abundance. It will singlehandedly increase the data we possess about where stars are located in space by thousands of times compared to all previous such measurements in history.

Gaia will measure the directions to 1 billion stars with a precision equivalent to measuring the different directions to the two edges of a grain of salt in Chicago as seen from Boston. For about 10 million stars, the precision will be better: matching the width of a salt grain in Hawaii as seen from here.

Gaia will measure each of these billion stars about 70 times during its planned five-year mission. This will allow data analysts to map the microscopic loops of "parallax motion" that stars appear to trace on the sky once a year due to our moving viewpoint on Earth as we circle the Sun. When you do the geometry for these loops, you get the most direct measurements of star distances possible.

 parallaxes have been measured from the ground since 1838, but only for stars nearby and not nearly as well as astronomers would like. Distances to farther stars used to be pathetically uncertain. This really mattered, for two reasons. The entire cosmic distance scale beyond the solar system -- not just for stars but nebulae, galaxies, and everything else -- was built on a foundation of nearby star distances. If you don't know an object's distance well, you usually can't tell its true size, brightness, energy output, mass, or much else about it very well either.

To address this problem, in 1989, the European Space Agency launched an earlier star-measuring craft named Hipparcos. In the clarity above Earth's atmosphere, it worked a revolution, raising the number of stars with reliable distances from a few thousand to more than 100,000 and reaching about 10 times farther out.

NASA planned to launch the next-generation star measurer, a satellite named FAME, in 2004. German astronomers planned a similar mission of their own named DIVA but dropped it because FAME would duplicate it. Then in 2002, NASA killed FAME because it broke its budget. So the planned second generation of space astrometry never happened.

Gaia was to be the third generation, which is why it will be such an enormous leap forward now. Its data-crunching teams expect to start issuing its first results in 2016 and the complete catalog for a billion stars in 2021. It can't come soon enough.

Alan M. MacRobert is a senior editor of Sky & Telescope magazine in Cambridge ( His Star Watch column appears the first Saturday of every month.