122nd Meeting
Speaker’s Night
Day:
Speaker: Ivan Semeniuk
The Astronomy of the Invisible
Ivan Semeniuk, Staff Astronomer at the Ontario
Science Centre has just started as the new Science Journalist at the U of T
Dunlop Institute. A popularizer of astronomy for years, he has worked for the
Discovery Channel and New Scientist magazine. He has a blog and weekly podcast
“The Universe in Mind” at http://www.di.utoronto.ca/journalist/ .
Ivan spoke of various aspects of the invisible in astronomy. He began by playing his first podcast where
he called professional astronomers to find out what they were doing at that
time. The podcast is Ivan’s IYA
project. He spoke of Galileo and his
discovery of Jupiter’s moon – the Medicean stars and the “handles” of
Saturn.
Until 1609, all things known in the universe could be
studied only with the naked eye and all thinkers were working with the same
database. Then, in the next 50 years, an
enormous number of discoveries were made due to people using telescopes. Afterwards, most astronomers had personal
observatories until 1911 when national observatories (
Is Mars dead or alive?
Mars is in the news. In the past 5 years rovers have told us that in the
past Mars was more hospitable than now.
There was surface water in the distant past, the best evidence being
sedimentary channels in the
The exoplanet
revolution began in 1995 when the first one was discovered. Now more than 300 exoplanets are
known. This year has been the most
exciting one so far. Just as stars are
seen in both the day and night but are not noticed in daytime due to the
brilliance of the sky, so planets are not easily noticed because of the brilliance
of the star. So far, planets have been
found either by transiting the star or by the Doppler shift in the star’s
spectrum. Now we have a third method of
detecting planets – by direct imaging. For
example, in September 2008, U of T astronomers, using the Gemini
telescope, blanked out the star HR 9799
and used infrared to see planets. In
1998, the Hubble Space Telescope imaged HR 9799 but the planets weren’t seen
then. The U of T team looked at other
HST stars, subtracted the light from HR 9799 and saw the planet. There are at least 100 stars in the HST
database where this could be done and creative mathematics can tease out the
planets.
In the last month, the COROT satellite has been
looking for transits of planets that are maybe like Earth. In February 2009, a star with an estimated
mass of 5 to 11 earths and a diameter 1.7 earth was found. The density is too great to be gas, so it is
either metal or less dense. What is it?
A super-earth? A hot Ganymede?
Supercritical water (hotter than the boiling point but under pressure)? The next step for exoplanet searching will be
the Kepler spacecraft due for launch on this night.
Has dark matter been
discovered? Discussions of dark matter are suddenly
reaching a fever pitch. The computer
simulation, Via Lactea, of a billion particles shows a huge halo of matter around the galaxy – a lump of dark
matter. The satellite PAMELA and the ATIC balloon experiment show many
positrons. WMAP shows excessive photons
from the centre of the galaxy which could be caused by dark matter. WIMPS (weakly interacting massive particles)
could be colliding with each other producing positrons and gamma rays as the
annihilation products. The Fermi space
telescope will give us the best view of the gamma ray sky, scanning the sky
every 2 days. It is hypothesized that
neutralino dark matter annihilation causes the gamma rays but there is a great
deal of noise. We want to see the dark matter signal stand out against the
strong signal from the galaxy. In
August, data from Fermi will be available to the public. The underground DAMA experiment in Italy
claims to detect more light flashes from purported WIMP interactions at one
time of the year supposedly caused by Earth going through a “dark matter
wind”. The biggest Canadian dark matter
detector is being planned at the SNO. The
Large Hadron Collider may be online again in the autumn and may produce
neutralinos. So, in the next 5 years we may know what dark matter is.
What was before the
beginning? In the next month, the Herschel spacecraft
may measure the microwave background. Microwaves
started soon after the Big Bang which is as far back as we can see. We look at the microwave background and infer
the state of the universe, that it is 74% dark energy. Planck (launch scheduled for April 16) will
see the background in much finer resolution as well as its polarization. Events before the microwave background may be
leaving their fingerprints on it i.e. inflation would cause ripples due to
gravity waves. The fine elements would
help distinguish between competing models such as inflation vs. higher dimension
spaces or membranes which can come together to for a Big Bang. The mission can distinguish between the two
theories.
Chris Malicki, Secretary