Planetarium Newsletter - January 2021

Cosmic Curiosities

“The light from a galaxy a billion light-years away, for instance, will take a billion years to reach us. It’s an amazing thing. The history is there for us to see. It’s not mushed up like the geologic record of Earth.”
- Margaret Geller, American Astrophysicist

Back to the Beginning

cosmic fossilsAstronomy is a little like geology. They both look back into time, hunting for fossils that tell us how we got here. Let’s take a trip back to the beginning of time. We’ll start with the first life fossils.

The oldest evidence for life on Earth comes from Western Australia. Lime-secreting cyanobacteria built up rocks mounds called stromatolites. They have been dated back in time to 3.5 billion years ago, the oldest life relics on Earth.

rocks on beachThe oldest known rocks were found in Canada, on the Hudson Bay in Northern Quebec. Geologists found an expanse of bedrock called the Nuvvuagittuq Greenstone Belt. Here, rocks dating back 4.28 billion years were detected. They first formed on a very young Earth, which formed 4.6 billion years ago.

In space, we can look back even further in time, before the Earth and life even came to be. Since stars and galaxies are so far, it takes a long time for their light to reach us; so we don’t see them as they are today, but as they were, millions and billions of years ago.

Around 9 billion years back in time, we detected Icarus, the farthest singular star our telescopes have ever seen. Tremendous telescopes would normally never see this star. But astronomers took advantage of gravitational lensing. This is where gravity from very massive objects bends spacetime and, therefore, amplifies the light from behind them. We see Icarus when the universe was still relatively young.


Uncovering the farthest known galaxy—a smaller with only one billion stars (our Milky Way has 200 billion)—was not easy. Again, we utilized a huge gravity well in space to magnify this more-distant galaxy. Astronomers also combined the power of the great Hubble and Spitzer space telescopes.

distant galaxyThe galaxy has been named MACS0647-JD and is located about 13.3 billion light years away. There is no fun nickname yet, so for now, I’ll call it the diminutive red glob. Its enormous distance means we are seeing a very young galaxy, born only 420 million years after the start of it all—the Big Bang.

Today, of course, this galaxy would be very old, and many of the stars would be long gone. Material from the death of these stars was used in the formation of the next generation of stars. It is the ultimate recycling program.

Looking at a very distant star or galaxy is like looking at a picture of a young Albert Einstein. Einstein is young, but the picture itself is now very old. Einstein left us in 1955, but his work on gravity keeps being used by many scientists today.

albert einsteinThe youngest picture of the universe is the Cosmic Microwave Background or CMB. It’s a map of the universe when it was just 378,000 years old. The splotchy colors you see reveal tiny temperature differences. Blue areas are about 1/10,000 degrees hotter than the red regions.

Today, this microwave radiation has traveled so far across billions of light-years of space that its temperature is 2.7 degree Kelvin, or -455 degrees Fahrenheit. When this energy first started its journey 13.7 billion years ago, it was 3,000 degrees Kelvin, or 5,000 degrees Fahrenheit.

cosmic microwave background

The CMB is the invisible leftover glow from when the universe first became transparent. It denoted a time when the universe had expanded enough that light could race across the cosmos in every direction. Our telescopes detect this faint radiation all around us. In fact, two percent of the fuzz on your TV set comes from the cosmic microwave background.

Temperature Solstice

snowy pine forestOn the winter solstice, December 21, the sun returned. Each day since, daylight hours have been increasing and the sun is climbing a little higher in the sky. So why does it stay so cold? Or, when does it finally get warmer (at least for us living in the northern hemisphere)?

The answer is around January 25. I call this the “cold temperature solstice.” This is basically the coldest day of the year, based on average temperatures recorded over history. The “warm temperature solstice” is around July 25, a month after the summer solstice on June 21. This is when the average temperature starts to decrease. Why does it take more than 30 days for the Earth to start warming up after sunlight starts increasing?

graph of milwaukee temperatures

Since the summer solstice, the northern hemisphere of the Earth has been receiving less and less sunlight or energy. Our planet's momentum has been swinging toward the cold for so long that it just can't stop on a dime and say, "Okay, it's the December solstice, time to warm up." There is a delay, so the Earth’s northern part keeps getting colder.

A way to understand the lag effect is a hot whistling tea kettle. When you pull it off the stove, the whistling will continue for a little bit, even though you removed it from the heat source.

Another reason it stays cold is the change in sunlight being small and gradual. We get less than 10 seconds of extra sunlight per day right after the solstice. By January 5, we northerners are getting one minute more of sunshine. By January 22, we start getting over two minutes of extra sunlight every day.   

So January 25 may be really cold this year, but celebrate anyway. The average temperature starts to go up! Though, of course, it will be a few more months before spring truly arrives, and probably another month before it’s warm enough for a cookout.

2021 Space & Sky Preview

space and sky 2021A rover landing on Mars tops the list for sky and space events in 2021. Perseverance left Earth on July 30. NASA hopes to land it safely on Thursday, February 18.

Wisconsinites will witness three eclipses in 2021. First, a partially eclipse moon can be seen just before sunrise on May 26. Then, another small one occurs on June 10, this time a solar eclipse. The sun will rise partially eclipsed by the moon for a short 28 minutes. Finally, a total lunar eclipse almost ( 97%) takes place in the middle of the night on November 19.

2021 Sky & Space Calendar

January 2: Earth at perihelion, closest point to the sun, 91.4 million miles

rocket flying through spaceJanuary 4: Latest Sunrise

January 23: Saturn at Superior Conjunction—behind the sun

January 28: Jupiter at Superior Conjunction—behind the sun

February: China’s Tianwen 1 (orbiter & rover) reaches Mars

February 6: 50th Anniversary of the First Golf Shot on the moon—Alan Shepard, Apollo 14

February 12: Chinese New Year—Year of the Ox

February 18: Perseverance Rover Lands in Jezero Crater on Mars

February 20: NASA’s Parker Solar Probe mission makes fourth Venus flyby

March 14: Spring ahead! Daylight Saving Time begins; Pi Day and Einstein’s Birthday

March 20: Spring begins at 4:37 a.m. CDT

March 26: Venus at superior conjunction—behind the sun as viewed from Earth

April 12: 60th Anniversary of First Person in Space—USSR’s Yuri Gagarin; 40th Anniversary of First Space Shuttle Launch

April 26-27: Super Full Moon

May 5: 60th Anniversary of First American Person in Space—Alan Shepard

May 26: Partial Super Moon Lunar Eclipse; Milwaukee, WI Times: 4:45 a.m. to 5:23 a.m. CDT

May 28: Venus and Mercury close in evening sky

June 10: Partial Solar Eclipse; Milwaukee WI times: 5:12 a.m. to 5:41 a.m. CDT

June 14: Earliest Sunrise

June 20: Summer Solstice starts at 10:32 p.m. CDT

June 27: Latest Sunset

July 5: Earth at aphelion, the farthest point from the sun, 94.5 million miles

July 4-5: Penumbral Lunar Eclipse (not visible in Wisconsin, North America)

June 12: Mars and Venus—very close in evening sky

July 22: Launch of NASA’s Double Asteroid Redirection Test (DART) to asteroids Didymos & Dimorphos

August 1: Saturn at opposition, visible all night

August 11-13: Perseid meteor shower peaks

August 19: Jupiter at opposition, visible all night

September 14: Neptune at opposition

September 22: Fall arrives with the autumnal equinox at 2:21 p.m. CDT

October 16: NASA’s Parker Solar Probe mission makes fifth Venus flyby; Launch of NASA’s Lucy flyby mission to multiple Trojan asteroids

October 31: Launch of NASA’s James Webb Space Telescope

November: Launch of NASA’s Artemis I to moon, test mission, no astronauts

November 4: Uranus at opposition

November 7: Fall back! Daylight Saving Time ends

November 19: Almost (97%) total lunar eclipse; Milwaukee, WI times: 1:18 a.m. to 4:47 a.m. CST

December 7: Earliest Sunset

December 12-14: Geminid meteor shower peaks

December 4: Total Solar Eclipse—Antarctica

December 21: Winter Solstice starts at 9:59 a.m. CST

Sky Sights  

Click maps to enlarge.

january skyJupiter and Saturn are in superior conjunction, or invisible behind the sun at the end of month. You can still catch them in the early evening at the start of January. By late February, you can observe these giant worlds in the morning skies.






january skyVenus keeps getting a little lower in the morning sky. It’s so bright, though, you should have no trouble viewing it if you have a clear path to the southeast sky. Watch for a waning crescent Moon near this hot world from January 9-11.






january skyTough-to-spot Mercury might be within reach in mid-January. A waxing crescent Moon shines near the smallest planet on January 14.







january skyperseverence rover on mars

Mars mixes with the first quarter Moon high in the south after sunset from January 19-21. Remember, we land the Perseverance rover on the red planet in mid-February. It left in late July 2020, a seven-month journey!

January Star Map 


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