Editor’s note: Dr. William Teets is the director of Vanderbilt University’s Dyer Observatory. In this interview, he explains what does and doesn’t happen during the winter solstice on Dec. 21. Another cosmic phenomenon is also going to occur on the same day called “the great conjunction,” where Saturn and Jupiter, both of which can be seen with the naked eye, will appear extremely close to one another.

What happens on the winter solstice?

The winter solstice this year happens on Dec. 21. This is when the Sun appears the lowest in the Northern Hemisphere sky and is at its farthest southern point over Earth – directly over the Tropic of Capricorn. For folks living at 23.5 degrees south latitude, not only does this day mark their summer solstice, but they also see the Sun directly over them at local noon. After that, the Sun will start to creep back north again.

The sequence of images below shows the path of the Sun through the sky at different times of the year. You can see how the Sun is highest in the Northern Hemisphere sky in June, lowest in December, and halfway in between these positions in March and September during the equinoxes.

The winter solstice is the shortest day in the Northern Hemisphere but not the day with the latest sunrise and earliest sunset. How is that possible?

The winter solstice doesn’t coincide with the latest sunrise or the earliest sunset. Those actually occur about two weeks before and two weeks after the winter solstice. This is because we are changing our distance from the sun due to our elliptical, not circular, orbit, which changes the speed at which we orbit.

If you were to look at where the Sun is at exactly the same time of day over different days of the year, you would see that it’s not always in the same spot. Yes, the Sun is higher in the summer and lower in the winter, but it also moves from side to side of the average noontime position, which also plays a role in when the Sun rises and sets.

One should also keep in mind that the seasons are due to the Earth’s axial tilt, not our distance from the Sun. Believe it or not, we are closest to the Sun in January.

What is ‘the great conjunction’?

Saturn and Jupiter have appeared fairly close together in our sky throughout the year. But on Dec. 21, Saturn and Jupiter will appear so close together that some folks may have a difficult time seeing them as two objects.

If you have a pair of binoculars, you’ll easily be able to spot both planets. In even a small telescope, you’d see both planets at the same time in the same field of view, which is really unheard of. That’s what makes this conjunction so rare. Jupiter and Saturn appear to meet up about every 20 years. Most of the time, however, they’re not nearly as close together as we’re going to see them on Monday, Dec. 21.

For a comparison, there was a great conjunction back in 2000, but the two planets were separated by about two full-Moon widths. This year, the orbits will bring them to where they appear to be about one-fifth of a full-Moon diameter.

We have been encouraging folks to go out and look at these planets using just their eyes between now and Dec. 21. You’ll actually be able to see how much they appear to move over the course of a single day.

The next time they will get this close together in our sky won’t be for another 60 years, so this is going to be a once-in-a-lifetime event for many people. In fact, the last time they got this close together was in the year 1623, but it was really difficult, if not impossible, to see them then because they appeared much closer to the Sun and set soon after it. Go back another 400 years to 1226 and this would have been the last time that we would have had a good view of this type of conjunction.

What advice would you give to people who want to see the great conjunction?

If weather permits at Dyer Observatory, we’ll be streaming a live view of the conjunction from one of the observatory’s telescopes, and I’ll be available to answer questions. Even if you don’t have a telescope or a pair of binoculars, definitely go out and check out this very rare alignment with your own eyes. Remember that they set soon after sunset, so be ready to view right at dusk!

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William Teets, Acting Director and Astronomer, Dyer Observatory, Vanderbilt University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Editor’s Note: With a coronavirus vaccination effort now underway, you might have questions about what this means for you and your family. If you do, This email address is being protected from spambots. You need JavaScript enabled to view it. and we will find a physician or researcher to answer them. Here, Dr. Mona Hanna-Attisha, a public health pediatrician whose research exposed the Flint, Michigan, water crisis, answers questions about the vaccine and allergies, and when kids might be able to get the vaccine.

If I have allergies, should I still get the vaccine?

If you have a history of allergies to food, pets, insects or other things, the Centers for Disease Control and Prevention recommends that you proceed with vaccination, with an observation period. If you have a history of severe allergic reaction, or what is called anaphylaxis, to another vaccine or injectable therapy, your doctor can do a risk assessment, defer your vaccination, or proceed and then observe you after vaccination. The only reason to avoid vaccination is a severe allergic reaction to any component of the COVID-19 vaccine. The CDC has specific recommendations for post-vaccine observation.

As the vaccine goes out to a broader population, how will adverse events be tracked?

The CDC and Food and Drug Administration encourage the public to report possible adverse events to the Vaccine Adverse Event Reporting System, or VAERS. This national system collects these data to look for adverse events that are unexpected, appear to happen more often than expected or have unusual patterns of occurrence. Anyone who has experienced an adverse event should report it to the system.

Reporting an adverse event is a crucial step to ensuring safety and to help the CDC monitor the vaccines. Safety is a top priority, and scientists and public health officials need to know about adverse reactions.

An adverse event is different in most cases from a typical vaccine side effect. Vaccines may cause a side effect, such as soreness at the injection site or redness. Adverse events are more serious and can sometimes be life-threatening. If you are unsure whether you have experienced a side effect or adverse event, you can still report the event.

Participants are given a fact sheet when they are vaccinated. Health care providers who vaccinate people will be required to report to VAERS certain adverse events following vaccination. In addition, under the terms of the emergency use authorization, health care providers also must follow any revised safety reporting requirements that may arise.

The CDC is also implementing a new smartphone-based tool called v-safe to check in on people’s health after they receive a COVID-19 vaccine. When you receive your vaccine, you should also receive an information sheet telling you how to enroll in v-safe. If you enroll, you will receive regular text messages directing you to surveys where you can report any problems or adverse reactions you have after receiving a COVID-19 vaccine.

When might kids younger than 16 be vaccinated?

It is likely to be several months. The currently authorized Pfizer and soon-to-be-authorized Moderna vaccine are not applicable for children. More research and clinical trials need to be done to include younger children in COVID-19 vaccine trials.

According to the American Academy of Pediatrics, Pfizer has enrolled children down to age 12 and submitted a request for emergency use authorization for vaccination down to age 16. Moderna, whose vaccine is expected to receive emergency use authorization from the FDA any day, is about to start a similar study.

In the United Kingdom, AstraZeneca has approval to enroll children ages 5 to 12 in clinical trials, but the pharmaceutical company has not yet enrolled any children in trials in the U.S.

Mona Hanna-Attisha, Professor of Medicine, Michigan State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.