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Transit of Venus June 5th

Due to the peculiarities of orbits of the two planets, Venus will pass in front of the Sun from our point of view twice in a few years every hundred years or so. This is called a transit. The last transit of Venus was in 2004, the next is the evening of June 5th 2012. The one after that is in about 105 years.

The event starts at about 5 PM CDT on June 5th and will proceed until well past our sunset. Of course, do not ever look directly at the Sun without proper protection. Venus will appear as a small dot on the surface of the Sun, too small to see without a properly filtered telescope.

Weather permitting, CAAS members will meet at the overflowing parking area across Highway 300 from the west field at about 6 PM to watch the transit (see map below). Later, as the Sun gets low we will move to the observation deck at the PMSP Visitor Center to watch until sunset.

More information can be found here or here.

NASA Selects Target Crater for Lunar Impact

Sept. 11, 2009: NASA’s Lunar Crater Observation and Sensing Satellite (LCROSS) is racing toward a double-impact on the moon at 7:30 am EDT on Oct. 9th. Today NASA announced exactly where the crash will take place.

The target crater is Cabeus A. It was selected after an extensive review of the best places to excavate frozen water at the lunar south pole.

Craters of interest around the lunar south pole. LCROSS is targeting Cabeus A. Image credit: NMSU/MSFC Tortugas Observatory.

Craters of interest around the lunar south pole. LCROSS is targeting Cabeus A. Image credit: NMSU/MSFC Tortugas Observatory

“The selection of Cabeus A was a result of a vigorous debate within the lunar science community. We reviewed the latest data from Earth-based observatories and our fellow lunar missions Kaguya, Chandrayaan-1, and the Lunar Reconnaissance Orbiter,” says Anthony Colaprete, LCROSS project scientist and principle investigator at NASA’s Ames Research Center. “The team is looking forward to wealth of information this unique mission will produce.”

LCROSS will search for ice by plunging its spent upper-stage Centaur rocket into the permanent shadows of Cabeus A, where water might be trapped in frozen form. The LCROSS satellite will then fly into the plume of debris kicked up by the impact and measure the properties of the plume before it also collides with the lunar surface.

The LCROSS team selected Cabeus A based on a set of conditions that includes favorable illumination of the debris plume for visibility from Earth, where astronomers will be watching closely. Cabeus A also has a high concentration of hydrogen (a constituent of water, H2O) and favorable terrain such as a flat floor, gentle slopes and the absence of large boulders.

Professional astronomers will use many of Earth’s most capable observatories to monitor the impacts. These observatories include the Infrared Telescope Facility and Keck telescope in Hawaii; the Magdalena Ridge and Apache Ridge Observatories in New Mexico and the MMT Observatory in Arizona; the newly refurbished Hubble Space Telescope; and the Lunar Reconnaissance Orbiter, among others.

Amateur astronomers can monitor the impact, too. Observing tips may be found here.

“Telescopes participating in the LCROSS Observation Campaign will provide observations from different vantage points using different types of measurement techniques,” says Jennifer Heldmann, lead for the LCROSS Observation Campaign at Ames. “These multiple observations will complement the LCROSS spacecraft data to help determine whether or not water ice exists in Cabeus A.”

During a media briefing Sept. 11, Daniel Andrews, LCROSS project manager at Ames, provided a mission status update: The spacecraft is healthy and has enough fuel to successfully accomplish all mission objectives. Andrews also announced the dedication of the LCROSS mission to the memory of legendary news anchor, Walter Cronkite, who provided coverage of NASA’s missions from the beginning of America’s manned space program to the age of the space shuttle.

“Dad would sure be proud to be part, if just in name, of getting humans back up to the moon and beyond,” says Chip Cronkite, son of the famed news anchor.

“We’re looking forward to October 9th,” Andrews says. “The next 28 days will undoubtedly be very exciting.”

Cabeus A, here we come!

Editor: Dr. Tony Phillips | Credit: Science@NASA

Red dot at bottom marks the spot

Red dot at bottom marks the spot

Shedding Light on Black Holes

July, 2009

By Tom Koonce

Antelope Valley Astronomy Club

Lancaster, California

Black Holes…  Just their name sounds like something out of science fiction.  Maybe this is one reason why they have been the focus of misconceptions and misguided theories.  This month, the theme of the International Year of Astronomy is centered on the objects that weigh heavily (pun intended) on the minds of theoretical physicists and leading astronomers… Black Holes.

First a bit of background on the subject.

The gravitational force exhibited by a celestial body is directly related to its mass and inversely proportional to the square of the distance which the object is away from that mass.  So how does a black hole generate its enormous gravity even though its mass is reduced to an infinitesimal point?

Consider a star with the mass and radius of the red supergiant Betelgeuse.  Under normal circumstances, an object could orbit the star at a distance outside of Betelgeuse’s stellar atmosphere.  But if the entire mass of Betelgeuse was compressed down to become a black hole and in the absence of Betelgeuse’s stellar atmosphere, the object could pass much closer to the black hole’s center of mass… so close, in fact, that the gravitational force it could experience would be incredibly high.

Another concept to realize is that if the Sun were to suddenly be replaced with a black hole of equal mass, the Earth would continue to orbit it in the exact same manner as it does today, except that the lack of sunlight would render the Earth incapable of sustaining life.

A common question that comes up during casual conversation about this subject is, “If I went through a black hole, where would I go?”  The straight-forward blunt answer?  “To your death!”   You literally would be torn to pieces by the gravitational tidal forces during your approach to the event horizon and then, with unerring certainty, what gelatinous mess remained would be squashed much, much flatter than a pancake as your remains fell deeper into the gravity well.  Black holes are not a mode of transportation to another universe, but they are efficient “matter compactors,” sweeping up all mass that passes too near.  Of course they can’t draw in matter from light years away, but as matter falls into a black hole it becomes (perhaps) infinitely compressed by its overwhelming gravitational force.

Imagine what a black hole looks like and you probably picture the graphic popularized by the media; a two dimensional plane with a funnel-shaped hole descending towards the black hole’s singularity.  This stylized perception of the three dimensional nature of the object has misled many people to think of a black hole as a hole in space, like a hole in the backyard, or perhaps a tunnel in space-time leading to other parts of our own universe.  The event horizon is a spherical region around the black hole, inside of which the black hole’s gravity is so strong that nothing can achieve escape velocity – nothing, not even light.  Because light can’t escape, space artists have envisioned the object as a black blob against a field of distant stars.  This black blob is surrounded by a fairly bright disk of material caught in the gravitational field.  Why is it bright?  As all of the dust and matter spirals in closer to the black hole it is rubbing against other matter, heating it up by friction until it gets to millions of degrees.  It is this dust outside of the event horizon that is radiating light.

What would a glimpse below the event horizon look like?  How important would it be to you to find out?  It would be a one-way trip to find out.  Nothing, not even light, can escape from below the event horizon… but photons of light could orbit the black hole.  Since there is an equivalent mass for the energy of a photon (E = mc2), light is affected by gravitational forces.  Photons can orbit a black hole if conditions are right.  Since there are photons continuously falling into black holes, many must get trapped in this manner.  We can’t see the photons because they are orbiting and not radiating outward and striking our retinas.  If we were somehow able to glimpse just below the event horizon, on that one way trip into gravitational flatness, I believe you would see bright light surrounding you; you would see photons instead of blackness.  Your final view would be of all of the light shed upon the black hole.