One interesting area of the sky that will be viewed by Gaia is the `blindspot’ found between the Sun and Earth’s orbit.
From Earth, we can only observe this area during the daytime (and even then only on clear days without cloud cover), but it is very hard to pick out small objects such as asteroids, because the Sun’s glare renders them virtually invisible.
These asteroids are sometimes moving near enough to Earth to cause concern, but we may not find out about them until they have moved far enough away from the Sun to be seen by a telescope. One particular large group of asteroids, known as the Atens, spends its time weaving between the Sun and Earth’s orbit.
We know very little about these families of asteroids following the same orbit. They regularly cross the Earth’s orbit, which makes them at least a potential threat, although most of them are not an actual danger to our planet. However, we need to understand why they are there, where they come from and what they are made of.
With the help of its bird’s eye view from space, and its unprecedented accuracy, Gaia is the ideal candidate for keeping track of the Atens, and similar families of asteroids coming close to our home.
But asteroids and Solar System objects will comprise only a tiny fraction of the objects that Gaia will study. Their detection is a by-product of the main goal of Gaia which is to precisely measure the location, motion and composition of several millions of stars in our Galaxy.
Armed with this information we will gain new insight into the life cycle of our Galaxy and its future.
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…there is no “blind spot” like the article mentions. The reason is that as the Earth orbits the sun, what was hidden is revealed. In other words, the sun no longer blocks a portion of space because now we’ve moved on. True, the article is correct about “seeing” objects near or between us and the sun — but by moving the satellite’s position, that problem is eliminated. The only problem I see is that the satellite is stuck in the L2 orbital position too close to earth.
The big news here is that there will be a computerized, three dimensional, color-coded, and otherwise detailed map of what Gaia sees. For me, this is EXTRA BIG NEWS, because I’ve never understood the astronomer’s concept of plotting objects in the heavens (true, could be lack of interest). For science-fiction writers who want to be accurate, knowing that this star is so many light years from that star would be invaluable and much more realistic to the reader.
What I didn’t know until recently was that the Milky Way (our galaxy) has four arms spirilling out from a central “sphere” about 60,000 light years in diameter. However, the arms are only about 100 light years thick. Earth’s position about half way out one arm leaves a lot of survey room nearby, especially with (they say) 100 billion plus stars in the Milky Way. I can’t wait for the data to be available.
Certainly increases the odds of intelligent life somewhere, eh? After all, there’s not much on Earth (especially among religious fanatics, politicians, tenure-seeking professors, or my exes)…
jon
You can find some maps that place stars in their three-dimensional positions at this site
It is true that the sun appears to block a certain portion of the background, and as the year progresses the sun appears to move against the background (best defined by the stars). Put another way, the sun comes between the earth and the object of interest briefly. What happens next, though, depends greatly on the object’s orbit. If the size of the orbit is greater than the earth’s (we’ll consider only small eccentricities), the earth will eventually come between the object and the sun. The object will then be quite visible high in the night sky. If it is an object in the solar system, it’s visible face will be fully illuminated by sunlight (no shadow) and it will be closer than it normally is. However, if the object’s orbit is smaller than earth’s, the earth can never come between the object and the sun, and it will never appear to be very far away from the sun. The smaller the orbit, the closer it comes to being always hidden in the sun’s glare, and more of its visible surface is in shadow the closer it comes in its orbit to earth. This is one of the reasons why it is easier to see Venus than Mercury, and why both are seen only in the morning or evening (not up all night). One way to decrease glare to see things closer to the sun is to get out of the atmosphere. Check out SOHO’s nice view of the sun. SOHO is in a halo orbit around L1; its LASCO instruments are used to find comets solar disturbances that would never be seen from earth’s surface (a mask covers the bright sun and a large area around it). Notice that there is still glare, which comes from dust near the sun as well as some solar material heaved off its surface (there’s also diffraction from the.mask and its support, cosmic ray strikes, pixel bleed from over-saturation, etc.). Space-based telescopes greatly reduce the size of the blind spot near the sun, but won’t eliminate it entirely.